Question

Shelly spent 10 minutes jogging and 20 minutes cycling and burned 300 calories. The next day, Shelly swapped times and did 20 minutes of jogging and 10 minutes of cycling, burning the same number of calories. How many calories were burned for each minute of jogging and how many for each minute of cycling?

Answer 1

10 calories were burned for each minute of jogging and 10 calories were burned for each minute of cycling.

Explanation:

Let be "j" the amount of calories Shelly burned for each minute of jogging and "c" the amount of calories Shelly burned for each minute of cycling.

Set up a system of equations:

`\left \{ {{10j+20c=300} \atop {20j+10c=300}} \right.`

You can apply the Elimination method: multiply the first equation by -2, then add the equations and solve for "c":

`\left \{ {{-20j-40c=-600} \atop {20j+10c=300}} \right.\\...............................\\-30c-300\\\\c=10`

Now, substitute the value of "c" into any original equation and solve for "j":

`10j+20(10)=300\\\\10j=300-200\\\\10j=100\\\\j=10`